Roll-up doors are commonly found on trucks and trailers, and on static structures (e.g., garage doors) as well.
These doors have a series of panels that are mounted for movement in a pair of opposed tracks between a lowered access-preventing vertical position, and a raised overhead out-of-the-way access-permitting horizontal position. Adjacent panels are hingedly joined to one another such that the various panels are mechanically connected in series. The tracks have a lower vertical portion, an intermediate arcuate or curved portion, and an upper overhead horizontal portion.
In recent years, there has been a movement to attempt to increase the size of the access opening through which cargo is moved into and out of a protected space (e.g., the cargo body, the interior of a static structure, etc.). The size of the access opening can be increased by (a) decreasing the width of the jambs on the structure on which the door is mounted so as to increase the width of the access opening, and/or by (b) decreasing the height of the overhead header so as to increase the height of the access opening. Such an increased-size access opening can allow for ingress and egress of larger-sized cargo and vehicles.
Typically, a counterbalance mechanism is mounted within the protected space, and is connected to the door to balance at least some of its weight. The counterbalance mechanism is typically mounted inside the protected space immediately behind the header.
While the vertical dimension of the header has been reduced to increase the size of the access opening, the three portions of the track (i.e., the vertical, arcuate and horizontal portions) must still allow for smooth continuous movement of the door between its closed and opened positions
To accommodate this, and to allow the raised door to be concealed behind the projected vertical height of a reduced-dimension header, it is known to mount a pair of pivoted hinges on the lowermost door panel. This type of hinge has one plate portion attached to the lowermost door panel, and has a second plate portion pivotally connected to the first plate portion. The roller is mounted on the distal marginal end portion of the second plate portion. When the door is in its lowered access-closing position, the second plate portion lies adjacent the first plate portion. However, when the door is raised to its overhead out-of-the-way position, the second plate portion may pivot relative to the first plate portion to allow the lowermost door panel to be concealed behind the projected header dimension while the roller on the second plate portion is still in the track arcuate portion.
One species of such a pivoted hinge structure is shown and described in US 2012/0125545 A1, the aggregate disclosure of which is hereby incorporated by reference. While this reference has such a pivoted hinge structure attached to the lowermost panel, it also has a generally L-shaped stop mechanism (indicated at 250 in such reference) that is mounted on the inside of the header, for preventing the lowermost door panel of the raised door from going past a predetermined position. (See, e.g., FIG. 7, and paragraphs [0099]-[0100] of this reference.)
While such a stop mechanism may be functional initially, it may become loose or deformed with use, and/or may permit the bottom door panel to move past its desired maximum desired position. In either event, the stop mechanism may possibly interfere with attempts to subsequently lower the door.